autofs: crash with SIGSEGV on try_remount using hierarchical map entries after service reload

Issue

• autofs crashes on reload (systemctl reload autofs) if hierarchical map entries are used, can be reproduced, using:

  # grep -v ^# /etc/auto.direct
  /required \
  / localhost:/playground2 \
  /sub1 localhost:/playground3 \
  /sub2 localhost:/playground4
  

• Trigger the mount :

  # grep requi /proc/mounts
  /etc/auto.direct /required autofs rw,relatime,fd=13,pgrp=33021,timeout=300,minproto=5,maxproto=5,direct,pipe_ino=10600557 0 0
  
  # find /required &> /dev/null
  
  # grep requi /proc/mounts
  /etc/auto.direct /required autofs rw,relatime,fd=13,pgrp=33021,timeout=300,minproto=5,maxproto=5,direct,pipe_ino=10600557 0 0
  /dev/mapper/rhel-root /required xfs rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0
  /etc/auto.direct /required/sub1 autofs rw,relatime,fd=13,pgrp=33021,timeout=300,minproto=5,maxproto=5,offset,pipe_ino=10600557 0 0
  /etc/auto.direct /required/sub2 autofs rw,relatime,fd=13,pgrp=33021,timeout=300,minproto=5,maxproto=5,offset,pipe_ino=10600557 0 0
  /dev/mapper/rhel-root /required/sub1 xfs rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0
  /dev/mapper/rhel-root /required/sub2 xfs rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0
  

• Now, edit /etc/auto.direct to remove one of the entries and reload the map:

  # vi /etc/auto.direct
  
  # grep -v ^# /etc/auto.direct
  /required \
  / localhost:/playground2 \
  /sub2 localhost:/playground4
  

• Reload :

  # systemctl reload autofs
  
  # systemctl status autofs
  ● autofs.service - Automounts filesystems on demand
  Loaded: loaded (/usr/lib/systemd/system/autofs.service; disabled; vendor preset: disabled)
  Active: failed (Result: signal) since Fri 2023-12-01 14:10:20 CET; 4s ago
  Process: 33082 ExecReload=/usr/bin/kill -HUP $MAINPID (code=exited, status=0/SUCCESS)
  Process: 33021 ExecStart=/usr/sbin/automount $OPTIONS --systemd-service --dont-check-daemon (code=killed, signal=SEGV)
  Main PID: 33021 (code=killed, signal=SEGV)